"I was meant to meet Amber and Chris (Mercedes and Kurt) the last time they were in London but I kept saying I was too busy because I was so nervous.

"Glee is a really important show actually. It's funny, but it's quite serious as well."

However, Adele rejected suggestions that she should cameo on the program, stating that she had been put off by an embarrassing guest appearance on Ugly Betty in 2009.

"I was such a mug on that show. I wasn't meant to say anything because you have to have an actor's visa in America. I was meant to turn up and mime my song but I turned up and they gave me a script and I had to speak as part of the storyline.

"Because I was in America, I put on a fake English accent. I don't know why! Everyone I know was taking the p**s out of me. Since then, I've had so many offers for other TV programs or films, and I'm just like, 'F**k off'."